var username = document.querySelector('.username');
var account = document.querySelector('.account');
var password = document.querySelector('.password');
var user_name = document.querySelector('.user_name');
var user_account = document.querySelector('.user_account');
var user_password = document.querySelector('.user_password');

username.onkeyup = function (e) {
    if (username.value != '') {
        user_name.style.visibility = 'hidden';
    }
    if (username.value == '') {
        user_name.style.visibility = 'visible';
    }
}

account.onkeyup = function (e) {
    if (account.value != '') {
        user_account.style.visibility = 'hidden';
    }
    if (account.value == '') {
        user_account.style.visibility = 'visible';
    }
}

password.onkeyup = function (e) {
    if (password.value.length >= 6) {
        user_password.style.visibility = 'hidden';
    }
    if (password.value.length < 6) {
        user_password.style.visibility = 'visible';
    }
}

var mybody = document.getElementById("bd");
mybody.addEventListener("click", function () {
    user_name.style.visibility = 'visible';
    user_account.style.visibility = 'visible';
    user_password.style.visibility = 'visible';
});
